Using Millis to Turn On/Off Relay for a set interval

[flashclass]

I have considered using a delay but I don't think that would solve the problem. I think that would just freeze those components for the delay time but I still encounter the issue of the unloader valve (ValveRelay4) turning off briefly every 15 seconds (warmInterval) rather than staying on for 15 seconds and turning off again until the psi<=Start is met again. Please see below.

@flashclass

if (psi<=Start){
 {digitalWrite (ConcRelay1 , HIGH);} // if psi is less than start setpoint turn on concentrator1
 {digitalWrite (ConcRelay2 , HIGH);} // if psi is less than start setpoint turn on concentrator2
 {digitalWrite (ValveRelay4 , HIGH);} // if psi is less than than start setpoint turn on solenoid valve
 psiStartTime = currentMillis; 
  }
 if ((unsigned long)(currentMillis - psiStartTime) >= warmInterval){ // allows concentrators to warm up prior to starting compressor, O2 purged through valve
 {digitalWrite (ValveRelay4 , LOW);}   //cuts power to solenoid after warmInterval time 
 {digitalWrite (CompRelay3 , HIGH);}         // if psi is less than start setpoint turn on compressor after warmInterval
 }

@gcjr

not clear what the RedEnd input should do. it prevents other actions for 1 minute, but it is not like on on off switch

The RedEnd input just puts all components of the system in a state which is safe to shut down the controller. The delay gives me 60 seconds to flip the off switch. This function is working as intended, to my surprise!

@Koepel I think your suggestion of using a boolean variable is a good one but I'm unsure how to implement it into my code given the example above. Do you think that would solve the the issue I'm experiencing and if so can you maybe give pseudo code example of how that might look?

Thanks very much to everyone for their suggestions, this is a great learning experience and I'm really thankful to have access to this communities knowledge set!